Automatic hovering gear for submarines



Nov. 23, 1965 N. WORTHING 3,219,005

AUTOMATIC HOVERING GEAR FOR SUBMARINES Filed Aug. 26, 1963 3 Sheets-Sheet, l

Nov. 23, 1965 N. WORTHING AUTOMATIC HOVERING GEAR FOR SUBMARINES 3 Sheets-Sheet 3 Filed Aug. 26, 1963 United States Patent C) 3,219,005 AUTOMATIC HOVERING GEAR FOR SUBMARINES Nicolas Worthing, London, England, assignor to The Harland Engineering Company Limited, Alloa, Scotland, a corporation of the United Kingdom Filed Aug. 26, 1963, Ser. No. 304,326 Claims priority, application Great Britain, Aug. 29, 1962, 33,17 8/ 62 12 Claims. (Cl. 114-16) This invention relates to hovering gear for submarines. A submarine when moving in a forward or reverse direction is maneuvered in the vertical plane by its hydroplanes and these can be used to hold the submarine at constant depth provided that it is moving. It is, however, desirable to be able to maintain a submarine within close limits at a chosen depth without the submarine moving in a forward or reverse direction. This is known as hovering and is performed by adjusting the buoyancy of the submarine, the hydroplane being inoperative without forward or reverse movement of the submarine.

A submarine has fuel oil storage tanks external to the pressure hull and vented to the sea. It will be appreciated that by transferring fuel oil from an external, sea vented tank to an internal submarine atmosphere vented tank or vice versa, the buoyancy of the submarine can be adjusted. Instead of transferring fuel oil between internal and external tanks, sea water or other liquid, possibly provided for buoyancy purposes only, may be used.

The present invention is concerned with mechanism for controlling the transfer of liquid between an internal, submarine atmosphere vented tank and an external sea vented tank whereby the buoyancy of the submarine may be adjusted.

According to the present invention mechanism for adjusting the buoyancy of a submarine whereby it may be maintained in a state of hover at a selected depth, comprises valve means to control the transfer of liquid between an internal tank vented to submarine atmosphere and an external tank vented to sea and actuator means to adjust the setting of the valve means in response to the error of depth from the selected depth, the vertical velocity and the vertical acceleration of the submarine.

The buoyancy adjusting mechanism may include a liquid flow circuit from the internal tank, through a pump, the valve means and back to the internal tank and a liquid flow line between the valve means and the external tank. The valve means may include a distributor valve and a differential valve by-passing said distributor valve, the distributor valve being adapted to control the flow of liquid to and from the external tank and the differential valve being adapted to divert back to the internal tank that quantity of liquid not required for transfer to the external tank whereby the 'fiow of liquid from the internal tank and through the pump is maintained at a substantially constant rate. The differential valve may comprise two slide valves in series with a compression spring between the two pistons of the valves. Preferably the liquid pressure in the flow line between the distributor valve and the external tank is applied to the free side of the piston of the second slide valve in the series. The force of the compression coil spring preferably is such that the pressure between the two pistons is p.s.i.g. below the pressure in the said flow line; The area of the piston of the first slide valve in the series may be half that of the piston of the second slide valve whereby the pressure acting on the free side of the piston in the first slide valve is 10 p.s.i.g. above the pressure in the said flow line.

To prevent oscillation over long periods of the dilferential valve and hammering in the different fluid flow lines, the liquid pressure in the flow line between the distributor 3,219,005 Patented Nov. 23, 1965 valve and the external tank may be applied to the free side of the piston of the second slide valve, through a stablising restriction.

The distributor valve may comprise a three-way slide valve.

The actuator means of the buoyancy adjusting mechanism of the present invention may comprise a hydraulic system, an adjustable valve to control the pressure existing in said system, means sensitive to the pressure difference between actual water pressure external of the submarine and water pressure corresponding to the selected depth of hover and adapted to vary, in accordance with the sensed pressure difference, the setting of the control valve and consequently the pressure existing in the hydraulic system, from a pre-set value and means responsive to variation in pressure in the hydraulic system, the rate of variation in said pressure and the change in rate of variation and adapted to adjust the setting of the distributor valve in accordance with the instantaneous values of these variables.

The control valve may comprise a ball valve acted on in one direction by a spring the bias of which is adjusted according to the desired depth of hover and in the other directionby means sensitive to the water pressure external of the submarine, the spring and pressure sensitive means acting against each other to position the ball valve in accordance with the pressure difference, if any, between the actual water pressure and the water pressure corresponding to the desired depth of hover.

The means responsive to the variation in pressure in the hydraulic system, the rate of variation in said pressure and the change in rate of variation, may comprise three hydraulic servo devices in series, the first being responsive to any variation in pressure in the hydraulic system, the second being responsive to any variation in pressure in the hydraulic system and also to the rate of variation in the setting of the first, and the third being responsive to any variation in the pressure of the hydraulic system and also to the rate of variation in the setting of the second whereby the setting of the third servo device is in accordance with the instantaneous values of the pressure in the hydraulic system, the rate of variation in that pressure and the change in rate of variation The invention is now described by way of example with reference to the accompanying drawings in which:

FIGURES 1(a) and 1(b) together show a schematic diagram of submarine buoyancy adjustment mechanism in accordance with the invention. FIGURE 1(b) is a continuation of FIGURE 1(a), the two FIGURES 1(a) and 1(b) to be read together as joined along the line Il at the right of FIGURE 1(a) and the line II at the left of FIGURE 1(b).

FIGURE 2 is an enlarged scale transverse section of a differential valve and distributor valve assembly which is shown schematically in FIGURE 1(b).

Referring to FIGURES 1(a) and 1(b) of the accompanymg drawings the pressure hull ofa submarine is indicated by thereference numeral 1 and mounted externally of thls is a tank 2 open to sea through a vent '3. A tank 4 is mounted internally of the pressure hull and is open to submarine atmosphere through a vent 5. The external tank 2 is connected through a filter 6 to a distributor valve 7 by a hover liquid flow line 8 having a hover line valve 9.

A pump 12, driven by a motor 13, draws liquid through a l1ne 14 from the internal tank 4 and passes it through a filter 15 and flow line 16 to a differential valve 17 and the distributor valve 7. A liquid return line 18 leads back from the differential valve 17 to the internal tank 4.

Referring to FIGURE 2, the differential valve 17 and distributor valve 7 are contained in a housing 20 having ports 21, 22 and 23. The port 21 is connected to the flow line 16, the port 22 to the flowline 18 and the port 3 23 to the flow line 8. As can be seen in FIGURE 2 the port 21 leads to a passageway forming, in effect an extension of the flow line 16 communicating with the differential valve 17 and distributor valve 7.

The distributor valve is a three-way slide valve comprising a sleeve 30 fixed within the housing 20. A slidable member 31 is mounted within the sleeve 30 and comprises two lands or heads 32 and 33 connected by a stem 34 so as to provide an annular chamber 35 between the two heads 32 and 33. A valve stem 36 is joined to the head 32 and passes through the wall of the housing and is connected to actuator means to be described hereinafter.

Three sets of ports are formed in the sleeve and these are designated 37, 38 and 39. The ports 37 open to the flow line 16, the ports 38, which communicate with the chamber 35, open to a chamber 40 around the sleeve 30 and communicating with the port 23, and the ports 39 open to a liquid passageway 41 in the housing 20 which can be brought into communication through the differential valve 17 with the port 22. A liquid communication is provided by a bore 42 between the top end of the head 32 and the bottom end of the head 33. A chamber 43 below the head 33 communicates through a line 44 with the liquid flow line 18 returning to the internal tank 4, thus providing relief to compensate for the swept volume of the valve stem 36.

When the slide member 31 of the distributor valve 7 is in a normal, midway position, as shown in FIGURE 2, the ports 37 and 39 in the sleeve 30 are closed by the heads 32 and 33. If the slide member 31 is moved up it will be seen that the ports 37 are open to the chamber which is open to the ports 38 so that liquid can flow from the flow line 16 through the ports 37 into the chamber 35, through the ports 38 into the chamber and thence through the hover flow line 8 into the external tank 2.

If the slide member 31 is lowered from its normal position as shown in FIGURE 2, the ports 39 are opened to the chamber 35 so that liquid can flow from the external tank 2 through the hover flow line 8 into the chamber 40, through the ports 38 into the chamber 35 and thence through the ports 39 into the passageway 41.

It will thus be appreciated that by appropriately setting the slide member 31 transfer of liquid to or from the external tank 2 at the desired rate can be accomplished.

For eflicient and instantaneous transfer of liquid from the internal tank 4 to the external tank 2 a supply of liquid under pressure must always be available at the ports 37 of the distributor valve 7. It follows, therefore, that provision must be made for the return to the internal tank of liquid in excess of that required for transfer to the external tank. This is accomplished, in such manner that there is always a constant supply of liquid at the required pressure at the ports 37, by the differential valve 17.

The differential valve 17 comprises two slide valves and 51 in series. The slide valve 50 comprises a sleeve 52 formed with ports 53 communicating with a chamber 54 leading to the passageway 41. A piston 55 of the slide valve 50 is slidably mounted within the sleeve 52. As can be seen in FIGURE 2, a stop 56 is fixed to the housing 20 and limits the upward movements of piston 55. The top surface of the piston 55 is in open communication with the flow line 16 and its bottom surface is in open communication with the passage 41.

The slide valve 51 comprises a sleeve 62 formed with ports 63 and fixed in the housing 20. The ports 63 communicate with a chamber 64 leading to the port 22 in the housing 20. A piston 65 is slidably mounted in the sleeve 62 and has a stop 66 to limit its upward movement. A compression coil spring 67 is mounted between the two pistons 55 and 65. The top surface of the piston 65 is in open communication with the passageway 41 and the bottom surface of the piston 65 is open to a chamber 68 which is connected through a flow line 69 with the hover fiow line 8. The two pistons 55 and 65 of the slide valves 50 and 51 can move independently of each other in accordance with the fluid pressure existing in the How line 16, the passageway 41 and the chamber 68.

As the liquid pressure existing in the hover flow line 8 is applied to the bottom surface of the piston 65, through the line 69 and chamber 68, it follows that the pressure between the two pistons 55 and 65 is automatically maintained below the hover line pressure by an amount equal to the spring 67 force divided by the lower piston area. The force of the spring 67 is so chosen that the pressure between the two pistons is 10 p.s.i. below the hover line pressure. The piston 55 is half the area of the piston 65 and it thus follows that the pressure above the piston 55 is automatically maintained at 20 p.s.i. above the pressure between the two pistons which is 10 p.s.i.g. below the hover line pressure. It follows, therefore, that the pressure above the piston 55 is automatically maintained at 10 p.s.i. above the hover line pressure.

These two controlled pressures of 10 p.s.i above and 10 p.s.i. below the hover line pressure are led to the ports 37 and 39 of the distributor valve 7 and ensure that the liquid flow in or out of the port 23 connected to the hover flow line 8 is directly proportional to the distributor valve displacement i.e. setting of the slide member 31 and is not affected by the depth at which the submarine is hovering.

To prevent oscillation of the pistons 55 and 65 of the differential slide valves 50 and 51 a stabilising restriction is provided in the line 69. This restriction is in the simple form of a screw 69a protruding into the line 69.

When the distributor valve 7 is fully open with the slide member 31 fully raised there is full out flow, of, for example g.p.m., in the hover flow line 8 with nothing returning through the fiow line 18 to the internal tank. When the distributor valve is fully closed with the slide member 31 lowered there is full inflow of, for example 80 g.p.m., in the hover fiow line 8 into the passageway 41 and this flow joins with the flow from the line 16 being by-passed through the differential valve 17 to give a return flow of 160 g.p.m. through the line 18 to the internal tank.

The setting of the distributor valve 7 is by way of actuator means, the mechanism of which is illustrated in FIGURE 1 within the dotted line 80. The actuator means is the brains to the mechanism according to the present invention and positions the distributor valve 7 according to the error of depth from the desired depth of hover, the vertical velocity and the vertical acceleration of the submarine.

To maintain a submerged submarine hovering with simple harmonic motion the buoyancy should be proportional to and in phase with the depth error. The buoyancy, however, is the integral of the distributor valve position and lags behind it by 90. It follows that the minimum requirement for stability of the submarine is that the distributor valve position should lead the depth error by 90. For the submarine to settle down at the required depth of hover this phase advance must be more than 90. In other words, the distributor valve must be displaced by an amount proportional to a certain combination of depth error, vertical velocity and vertical acceleration.

The actuator means 80 comprises a hydraulic system having a supply of oil in a reservoir 81. A pump 82 draws oil from the reservoir 81 and passes it through a filter 83 to a reducing valve 84. A pressure relief valve 85 is connected between the pump 82 and the filter 83. The pump is driven by a motor 86. From the reducing valve 84 the oil flows through a line 87 to a ball valve 88 from which it can escape back to the reservoir 81. A second oil flow line 89 leads from the reducing valve 84 and is connected to each of three servo devices, A, B and C. The reducing valve 84 is set to drop 35 p.s.i. so that r the pressure in line 89 is normally 81 p.s.i.g. and is used to operate the hydraulic controls of the servo devices A, B and C.

A pivoted actuator arm 95 bears against the ball valve 88 and is biassed in one direction, to allow the valve to open, by a compression coil spring 96 and in the other direction, to allow the valve to close, by pressure bellows 97. The spring 96 is located between the actuator arm 95 and an adjustable support 98. The positioning of the support 98 may be varied by a captive screw mechanism 99 having threaded connection to the support 98. The bellows 97 are connected to external sea pressure by a line 100.

Leading from the ball valve 88 are oil flow lines 101, 102 and 103. If the ball valve is fully closed so that there is no escape of oil back to the reservoir 81 then all the oil leaves the ball valve through these three lines 101, 102 and 103. If the ball valve is open then a portion of the oil escapes back to the reservoir 81 and the remainder, depending upon the setting of the valve, flows through the lines 101, 102 and 103. The ball valve 88 is loaded by the bellows 97 less the force of the spring 96, which is set for the required depth of hover. It will thus be appreciated that any error in the depth of hover is sensed by the ball valve so that its setting is appropriately adjusted thereby varying the quantity and pressure of the oil flowing through the lines 101, 102 and 103. When the actual depth of the submarine is equal to the pre-set depth of hover, the control signal pressure in the lines 101, 1 02 and 103 is a value of 46 p.s.i.g. or 104 feet of sea water, but until this system settles down the pressure in said lines is 104+h feet, where h is the depth error, the areas of ball valve seal and bellows being equal.

A visual indicating gauge 105, showing the depth error, is connected by a line 106 to the line 101.

a Each servo device A, B and C comprises a pilot valve 110, a return spring 111, a follower 112, a return motion lever 113 and a slave piston 114 in a cylinder 115.

The pilot valve comprises a slide 120 formed with three annular valve chambers 121 and slidable in a sleeve 122. Oil inlet flow lines 123 and 124 open into the sleeve 122 and are connected respectively to the flow lines 89 and 101. The connection of the flow lines 123 and 124 is the same in the servo devices A and B but is different, as will be described, in the servo device C.

A head 125 of the slide 120 opens to a chamber 126 supplied with oil through a throttle 127 from the flow line 103.

A flow line 130 is connected between the sleeve 122 and a chamber 131 in the cylinder 115 below the slave piston 114. A drain port 132 opens from the sleeve 122 of the pivot valve 110.

Concerning the pilot valve 110 of the servo device A, it will be appreciated that depending upon the setting of the slide 120, oil can flow from the line 123 through the line 130 into the chamber 131 or from the chamber 131 through the line 130 and out through the drain 132.

The servo device B is of the same construction and has the same flow line connections as the servo device A except (1) that a chamber 135 in the cylinder 115 above the slave piston 114 of the servo device A, is connected through a line 136 to the chamber 126 above the head 125 of the slide 120 constituting part of said servo device B; and (2) that the flow line102 leads to the throttle 127 of the servo device B. t

The construction of the servo device C is the same as that of the servo devices A and B but the connection of the different flow oil lines is different. With the servo device C, the throttle 127 is in communication with the flow line 101 and the chamber 126 above the head 125 of the slide 120 is in communication with the flow line 136 from the chamber 135 above the slave piston 114 of the servo device B. The oil pressure in the line 87 is led through a line 140 through two branch lines 141 and 142 to the sleeve 122 of the pilot valve 110 of the servo deside of the reducing valve 84, opens into the said sleeve 122, through a line 143. The chamber 131 below the sleeve piston 114 of the servo device C is connected to the sleeve 122 through the line 130 and the chamber 135 above the slave piston 144 also is connected to the sleeve 122 through line 136.

The return motion lever 113 of the servo device C is connected by a link 150 to the valve stem 36 of the distributor valve 7. a

With each servo device A, B or C the slave piston 114 thereof automatically assumes a position depending on the oil pressure in the chamber 126 applied to the head of the slide 120. In the case of servo devices A and B, if the pressure in this chamber 126 rises the slide 120 moves down and admits oil under pressure through the line to the chamber 131 below the slave piston 114. The slave piston 114 thus rises swinging the return motion lever 113 upwards. This causes the follower 112 to rise and compresses the return spring 111 proportional to the increase in pressure and then slide 120 returns to its neutral position and stops further motion. If the slide 120 rises becauseof a fall in pressure in the chamber 126 the line 130 is connected with the drain port 132 so that the chamber 131 is drained and the slave piston 114 falls. The return mot-ion lever 113 is thus swung downwards so that the follower 112 falls to expand the return spring 11 proportional to the drop in pressure and then the slide 120 returns to its neutral position and stops further action. The servo device C functions in basically the same manner but when its slide 120 rises chamber 131 isconnected to comparatively low pressure in line 141 and the chamber to comparatively high pressure in line 143, so that the slave piston 114 falls, or vice versa.

The elevation of the slave piston 114 is thus at all times proportional to the pilot pressure applied in the chamber 126 to the head 125 of the slide 120. The mid position of the slave piston corresponding to a predetermined pressure in the chamber 126 of the pilot valve which is chosen to correspond to 104 feet of sea water pressure.

The three servo devices A, B and C are connected in series and through the link are coupled to the distributor valve 7. These servo devices generate a pressure signal depending on the setting of the ball valve 88, which corresponds to the depth error of hover of the submarine, the vertical velocity and the vertical acceleration of the submarine, in the following manner:

Control pressure of a 104-Hz feet is applied, through the line 103 and throttle 127 in the chamber 126 of the servo device A and the slave piston 114 thereof is dis-, placed from its mid position by a distance proportional to the depth error of h feet. For the sake of simplicity in this description it will be assumed that h is a positive value'namely that the submarine is below the desired depth of hover and, therefore, the slave piston is displaced upwardly from its mid position. If the depth is increasing the oil above the slave piston 114 is being forced out into the chamber 126 of the second servo device B and is escaping through the throttle 127 thereof into the flow line 102 in which the pressure drop is A.dl1/dt feet, where A is a constant depending on the throttle setting, and dh/dt is the downward velocity of the submarine. If the submarine is rising it will be appreciated that the flow through the throttle 127 of the servodevice B reverses and the derivative pressure is negative.

The pressure acting in the chamber 126 of the servo device B is, therefore, 104+h+A.dh/dt feet and the second slave piston 114 Le. the slave piston of the servo device B, is displaced upwards from its mid position by a distance proportional to h+A.dh/dz. The oil above the slave piston 114 of the servo device B escapes to the control pressure line 101 through the throttle 127 of the third servo device C and the pressure drop in this throttle is B.d(h|A.dh/dt)dt, or B.dh/dt+A.B.d h/dt feet where B is another constant depending on the setting 7 of the throttle 127 of the servo device C. and d h/a't is the downward acceleration of the submarine. Again if the submarine is rising the flow reverses and the derivative pressure is negative.

The pressure acting in the chamber 126 of the third servo device C is, therefore, 104+h+b.dh/dt-[-A.B. d lz/dt feet and the third slave piston 114 i.e. the slave piston of the servo device C, is displaced upwards from its mid position by a distance proportional to h+b. dh/a't+A.B.d h/Dt namely proportional to the depth of error, the vertical velocity and vertical acceleration of the submarine from its desired depth of hover.

The slave piston 114 of the servo device C is connected, by the link 150, to the stem 36 of the distributor valve 7 and the slide member 31 thereof is thus displaced by an amount proportional to the desired combination of depth error, vertical velocity and vertical acceleration.

It is desirable that the submarine should reach its desired depth of hover as soon as possible and for this purpose smoothing or dampening devices are provided. These are in the form of bellows accumulators indicated at 160 and the throttle 127 of the first servo device A. The purpose of these is to smooth out the effects of wave motion at depth and if not provided there would be a parasitic signal producing undesired amplitudes of the distributor valve 7.

To minimize friction Within the servo devices A, B and C the followers 112 thereof are rotated by gearing from the drive motor 86 of the pump 82 and transmit rotation to their respective slides 120 through the return springs 111. This rotation overcomes friction in the pilot valves and greatly increases the sensitivity.

For satisfactory operation it is desirable to maintain the throttle coeificients A and B reasonably constant. Without temperature control the viscosity of the oil in the reservoir 81 and circulating through the hydraulic system of the actuator means would vary over a wide range and there would be corresponding changes in the throttle coefficients A and B which possibly would be intolerable.

The temperature of the actuator means is controlled by two electric heaters 170 and 171 with their individual thermostats 172 and 173 and contractors so that the vital temperature at the throttles 127 of the servo devices A, B and C is maintained constant for example, 110 F.

To bring a submarine into a tate of hover at a desired depth the submarine first of all is brought down to the required depth of hover in the conventional manner by the use of the hydroplanes. The trim of the submarine is adjusted until the submarine is maintained at that depth with the hydroplanes level. The pump 82 of the actuator is brought into operation and the setting of the control spring 96 adjusted until the gauge 105 reads zero. The actuator means is thus set to the depth at which the submarine is being held by its hydroplanes. The propulsion motors of the submarine are then stopped and final adjustment made to the trim as the submarine slows down. When the depth can no longer be maintained by the hydroplanes then the pump 12 is started and automatic hover control is in operation.

What is claimed is:

1. Mechanism for adjusting the buoyancy of a submarine having a hull whereby said submarine may be maintained in a state of hover at a selected depth, said mechanism comprising an internal tank mounted inside the submarine hull and being vented to the interior of said hull; an external tank mounted on and outside said hull and being vented at sea; a unidirectional flow pump having a substantially constant rate of discharge and having its intake in communication with said internal tank; means including liquid flow circuit means and valve means therein for selectively providing (1) valve-controlled fiow of liquid from said internal tank through said pump to said valve means and thence back to said internal tank and (2) valve controlled flow of liquid from said internal tank through said pump to said valve means and thence to said external tank; said valve means comprising a distributor valve controlling the flow of liquid to and from said external tank and a differential valve controllable for diverting back to said internal tank that quantity of liquid discharged by said pump which is not required for transfer to said external tank for effecting the required buoyancy adjustment, the differential valve in turn comprising a first and a second slide valve in series, said slide valves each including a slidable piston, each of said pistons having a first side facing a corresponding first side of the other piston and a free side, and a compression spring between and engaging said first sides of said pistons; and actuator means connected to said valve means and being operable in response to the error in depth, from the selected depth, the vertical velocity and the vertical acceleration of the submarine for operating said valve means whereby selectively to cause liquid to flow from said internal tank through said valve means and back to said internal tank or from said internal tank to said external tank to efiect the required buoyancy adjustment of the submarine.

2. Mechanism for adjusting the buoyancy of a submarine having a hull whereby said submarine may be maintained in a state of hover at a selected depth, said mechanism comprising an internal tank mounted inside the submarine hull and being vented to the interior of said hull; a external tank mounted on and outside said hull and being vented to sea; a unidirectional flow pump having a substantially constant rate of discharge and having its intake in communication with said internal tank; means including liquid flow circuit means and valve means therein for selectively providing (1) valve-controlled flow of liquid from said internal tank through said pump to said valve means and thence back to said internal tank and (2) valve controlled flow of liquid from said internal tank through said pump to said valve means and thence to said external tank; said valve means comprising a distributor valve controlling the flow of liquid to and from said external tank and a differential valve controllable for diverting back to said internal tank that quantity of liquid discharged by said pump which is not required for transfer to said external tank for effecting the required buoyancy adjustment, the differential valve in turn comprising a first and a second slide valve in series, said slide valves each including a slidable piston, each of said pistons having a first side facing a corresponding first side of the other piston and a free side, and a compression spring between and engaging said first sides of said pistons; said liquid flow circuit means including a fiow line between said distributor valve and said external tank, and means for applying pressure from said flow line to the free side of the piston of said second slide valve; and actuator means connected to said valve means and being operable in response to the error in depth, from the selected depth, the vertical velocity and the vertical acceleration of the submarine for operating said valve means whereby selectively to cause liquid to flow from said internal tank through said valve means and back to said internal tank or from said internal tank to said external tank to effect the required buoyancy adjustment of the submarine.

3. Mechanism according to claim 2 wherein the force of said compression spring is such that the pressure difference between said two pistons is 10 p.s.i. below the pressure in said fiow line.

4. Mechanism according to claim 3 wherein the area of the piston of said first slide valve is half that of the piston of said second slide valve, whereby the pressure acting on the free side of the piston of said first slide valve is 10 p.s.i. above the pressure in said flow line.

5. Mechanism according to claim 4 wherein said means for applying pressure from said flow line to the free side of the piston of said second slide valve includes a stabilizing restriction.

6. Mechanism according to claim 1 wherein said distributor valve is a three-way slide valve.

7. Mechanism for adjusting the buoyancyof a submarine having a hull whereby said submarine may be maintained in a state of hover at a selected depth, said mechanism comprisingan internal tank mounted inside the submarine hull and being vented to the interior of said hull; an external tank mounted on and outside said hull and being vented to sea; a unidirectional flow pump having a substantially constant rate of discharge and having its intake in communication with said internal tank; means including liquid flow circuit means and valve means therein for selectively providing (1) valve-controlled flow of liquid from said internal tank through said pump to said valve means and thence back to said internal tank and (2) valve controlled flow of liquid from said internal tank through said pump to said valve means and thence to said external tank; said valve means comprising a distributor valve controlling the flow of liquid to and from said external tank and a difierential valve controllable for diverting back to said internal tank that quantity of liquid discharged by said pump which is not required for transfer to said external tank for effecting the required buoyancy adjustment; and actuator means connected to said valve means and being operable in response to the error in depth, from the selected depth, the vertical velocity and the vertical acceleration of the submarine for operating said valve means whereby selectively to cause liquid to flow from said internal tank through said valve means and back to said internal tank or from said internal tank to said external tank to effoot the required buoyancy adjustment of the submarine; said actuator means comprising a hydraulic system, an adjustable control valve for controlling the pressure in said hydraulic system, means for sensing the pressure difference between the actual water pressure external of the submarine and the water pressure corresponding to the selected depth of hover and being operable in accordance with the sensed pressure difference for varying the setting of said adjustable control valve and thereby varying the pressure in said hydraulic system from a pre-set value, and means responsive to the variation in pressure in said hydraulic system, the rate of variation in said pressure and the change in rate of variation in said pressure for adjusting the setting of said distributor valve in accordance with the instantaneous values of the pressure in the hydraulic system, the rate of variation in said pressure and the change in rate of variation in said pressure.

8. Mechanism for adjusting the buoyancy of a submarine having a hull whereby said submarine may be maintained in a state of hover at a selected depth, said mechanism comprising an internal tank mounted inside the submarine hull and being vented to the interior of said hull; an external tank mounted on and outside said hull and being vented to sea; a unidirectional flow pump having a substantially constant rate of discharge and having its intake in communication with said internal tank; means including liquid flow circuit means and valve means therein for selectively providing (1) valve-controlled fiow of liquid from said internal tank through said pump to said valve means and thence back to said internal tank and (2) valve-controlled flow of liquid from said internal tank through said pump to said valve means and thence to said external tank; said valve means comprising a distributor valve controlling the flow of liquid to and from said external tank and a differential valve controllable for diverting back to said internal tank that quantity of liquid discharged by said pump which is not required for transfer to said external tank for effecting the required buoyancy adjustment; and actuator means connected to said valve means and being operable in response to the error in depth, from the selected depth, the vertical velocity and the vertical acceleration of the submarine for operating said valve means whereby selectively to cause liquid to flow from said internal tank through said valve means and back to said internal tank or from said internal tank to said external tank to effect the required buoyancy adjustment of the submarine; said actuator means comprising a hydraulic system, an adjustable control valve for controlling the pressure in said hydraulic system, said adjustable control valve having a movable valve ball, a spring biasing said valve ball in one direction, means for adjusting the bias of said spring in accordance with the desired depth of hover, means sensitive to water pressure external of the submarine urging said valve ball in the opposite direction, said spring and said means sensitive to water pressure acting against each other to position said valve ball in accordance with the pressure dilference between the actual water pressure external of the submarine and the water pressure corresponding to the desired depth of hover and thereby varying the pressure in said hydraulic system from a pre-set value, and means responsive to the variation in pressure in said hydraulic system, the rate of variation in said pressure and the change in rate of variation in said pressure for adjusting the setting of said distributor valve in accordance with the instantaneous values of the pressure in the hydraulic system, the rate of variation in said pressure and the change in rate of variation in said pressure.

9. Mechanism according to claim 8 wherein said means responsive to the variation in pressure in said hydraulic system, the rate of variation in said pressure and the change in rate of variation in said pressure comprises three hydraulic servo devices in series, the first of said servo device being responsive to variation in pressure in said hydraulic system, the second of said servo devices being responsive to variation in pressure in said hydraulic system and also to the rate of variation of the setting of the first of said servo devices, and the third of said servo devices being responsive to variation in pressure in said hydraulic system and also to the rate of variation in the setting of said second of said servo devices, whereby the setting of said third of said servo devices is in accordance with the instantaneous values of the pressure in said hydraulic system, the rate of variation, of that pressure and the change in rate of variation thereof.

10. Mechanism according to claim 9 wherein each of said servo devices comprises a pilot valve including a pilot valve piston; a slave piston cylinder; a slave piston in said slave piston cylinder; a return motion lever connected to said slave piston; a follower cooperating with said return motion lever; and a spring interposed between said pilot valve piston and said follower, whereby said slave piston is movable to a position in said slave piston cylinder in dependence upon hydraulic pressure applied to said pilot valve piston.

11. Mechanism according to claim 7 wherein said means responsive to the variation in pressure in said hydraulic system, the rate of variation in said pressure and the change in rate of variation in said pressure comprises three hydraulic servo devices in series, the first of said servo devices being responsive to variation in pressure in said hydraulic system, the second of said servo devices being responsive to variation in pressure in said hydraulic system and also to the rate of variation of the setting of the first of said servo devices, and the third of said servo devices being responsive to variation in pressure in said hydraulic system and also to the rate of variation in the setting of said second of said servo devices, whereby the setting of said third of said servo devices is in accordance with the instantaneous values of the pressure in said hydraulic system, the rate of variation of that pressure and the change in rate of variation thereof.

12. Mechanism according to claim 11 wherein each of said servo devices comprises a pilot valve including a pilot valve piston; a slave piston cylinder; a slave piston in said slave piston cylinder; a return motion lever connected to said slave piston; a follower cooperating with said return motion lever; and a spring interposed between said pilot valve piston and said follower, whereby said 11 i 12 slave piston is movable to a position in said slave piston 2,526,406 10/1950 Pfauser et al. 137596.12 cylinder in dependence upon hydraulic pressure applied 2,887,976 5/1959 Hanna et a1. 11416 to said pilot valve piston. 2,972,972 2/ 1961 Allen 11416 References Cited by Examine 5 MILTON BUCHLER, Primary Examiner.

UNITED STATES PATENTS FERGUS s. MIDDLETON, Examiner.

2,488,286 11/1949 Glenny. 

1. MECHANISM FOR ADJUSTING THE BUOYANCY OF A SUBMARINE HAVING A HULL WHEREBY SAID SUBMARINE MAY BE MAINTAINED IN A STATE OF HOVER AT A SELECTED DEPTH, SAID MECHANISM COMPRISING AN INTERNAL TANK MOUNTED INSIDE THE SUBMARINE HULL AND BEING VENTED TO THE INTERIOR OF SAID HULL; AN EXTERNAL TANK MOUNTED ON AND OUTSIDE SAID HULL AND BEING VENTED AT SEA; A UNIDIRECTIONAL FLOW PUMP HAVING A SUBSTANTIALLY CONSTANT RATE OF DISCHARGE AND HAVING ITS INTAKE IN COMMUNICATION WITH SAID INTERNAL TANK; MEANS INCLUDING LIQUID FLOW CIRCUIT MEANS AND VALVE MEANS THEREIN FOR SELECTIVELY PROVIDING (1) VALVE-CONTROLLED FLOW OF LIQUID FROM SAID INTERNAL TANK THROUGH SAID PUMP TO SAID VALVE MEANS AND THENCE BACK TO SAID INTERNAL TANK AND (2) VALVE CONTROLLED FLOW OF LIQUID FROM SAID INTERNAL TANK THROUGH SAID PUMP TO SAID VALVE MEANS AND THENCE TO SAID EXTERNAL TANK; SAID VALVE MEANS COMPRISING A DISTRIBUTOR VALVE CONTROLLING THE FLOW OF LIQUID TO AND FROM SAID EXTERNAL TANK AND A DIFFERENTIAL VALVE CONTROLLABLE FOR DIVERTING BACK TO SAID INTERNAL TANK THAT QUANTITY OF LIQUID DISCHARGED BY SAID PUMP WHICH IS NOT REQUIRED FOR TRANSFER TO SAID EXTERNAL TANK FOR EFFECTING THE REQUIRED BUOYANCY ADJUSTMENT, THE DIFFERENTIAL VALVE IN TURN COMPRISING A FIRST AND A SECOND SLIDE VALVE IN SERIES, SAID SLIDE VALVES EACH INCLUDING A SLIDABLE PISTON, EACH OF SAID PISTONS HAVING A FIRST SIDE FACING A CORRESPONDING FIRST SIDE OF THE OTHER PISTON AND A FREE SIDE, AND A COMPRESSION SPRING BETWEEN AND ENGAGING SAID FIRST SIDES 